Heping Zhang

Bio: Heping Zhang is an academic researcher from Lanzhou University. The author has contributed to research in topics: Bipartite graph & Cubic graph. The author has an hindex of 31, co-authored 227 publications receiving 5035 citations. Previous affiliations of Heping Zhang include Commonwealth Scientific and Industrial Research Organisation & University of Reading.

Water-yield relations and water-use efficiency of winter wheat in the North China Plain

Abstract: Limited precipitation restricts yield of winter wheat (Triticum aestivum L.) grown in the North China Plain. Water stress effects on yield can be avoided or minimized by application of irrigation. We examined the multiseasonal irrigation experiments in four locations of the piedmont and lowland in the region, and developed crop water-stress sensitivity index, relationship between seasonal evapotranspiration (ET) and yield, and crop water production functions. By relating relative yield to relative ET deficit, we found that the crop was more sensitive to water stress from stem elongation to heading and from heading to milking. For limited irrigation, irrigation is recommended during the stages sensitive to water stress. Grain yield was 258–322 g m−2 in the piedmont and 260–280 g m−2 in the lowland under rainfed conditions. The corresponding seasonal ET was 242–264 mm in the piedmont and 247–281 mm in the lowland. Irrigation significantly increased seasonal ET and therefore grain yield as a result of increased kernel numbers per m−2 and kernels per ear. On average, one irrigation increased grain yield by 21–43% and two to four irrigations by 60–100%. Grain yield was linearly related to seasonal ET with a slope of 1.15 kg m−3 in the lowland and 1.73 kg m−3 in the piedmont. Water-use efficiency was 0.98–1.22 kg m−3 for rainfed wheat and 1.20–1.40 kg m−3 for the wheat irrigated 2–4 times. Grain yield response to the amount of irrigation (IRR) was developed using a quadratic function and used to analyze different irrigation scenarios. To achieve the maximum grain yield, IRR was 240 mm in the piedmont and 290 mm in the lowland. When the maximum net profit was achieved, IRR was 195 mm and 250 mm in the piedmont and lowland, respectively. The yield response curve to IRR showed a plateau over a large range of IRR, indicating a great potential in saving IRR while maintaining reasonable high levels of grain yield.

Water Use Efficiency of Rainfed and Irrigated Bread Wheat in a Mediterranean Environment

Abstract: In West Asia and North Africa, shortage of water limits wheat (Triticum aestivum L.) production. Current irrigation practices aim at maximizing grain yield, but achieve lower return for the water consumed. Maximizing water use efficiency (WUE) may be more suitable in areas where water, not land, is the most limiting factor. We examined the effects of various levels of supplemental irrigation (SI) (rainfed, 1/3 SI, 2/3 SI, full SI), N (0, 5, 10, 15 g N m -2 ), and sowing time (Nov., Dec., Jan.) on evapotranspiration (ET) and WUE of wheat. WUE was calculated for rain (WUE,), for total water (gross: rain + irrigation) (WUE g ), and for SI water only (WUE SI ). ET ranged from 246 to 328 mm for rainfed crops, with grain yield ranging from 130 to 270 g m -2 and total dry matter from 380 to 1370 g m -2 . Irrigated crops had ET of 304 to 485 mm, with grain yield of 170 to 500 g m -2 . The degree to which water supply limits grain yield was indicated by the ratio of pre- to post-anthesis ET (2.1-2.4:1). The SI treatments significantly increased WUE g : from 0.77 to 0.83 to 0.92 kg m -3 in November and December sowings for 1/3 SI and from 0.77 to 0.92 kg m -3 in November sowing for 2/3 SI. The highest WUE g and WUE SI were achieved at 1/3 to 2/3 SI. WUE was substantially improved by applying 5 and 10 g N m -2 , with little increase for higher rates. Delaying sowing had a negative effect on WUE for both irrigation and rainfed conditions. In this rainfed Mediterranean environment, WUE can be substantially improved by adopting deficit SI to satisfy up to 2/3 of irrigation requirements, along with early sowing and appropriate levels of N.

Water-use efficiency and transpiration efficiency of wheat under rain-fed conditions and supplemental irrigation in a Mediterranean-type environment

Abstract: Growth and water use were measured in wheat (Triticum aestivum L.) grown in northern Syria in a typical Mediterranean climate over five seasons 1991/92–1995/96. Water use was partitioned into transpiration (T) and soil evaporation (Es) using Ritchie's model, and water-use efficiency (WUE) and transpiration efficiency (TE) were calculated. The aim of the study was to examine the influence of irrigation and nitrogen on water use, WUE and TE. By addition of 100 kg N ha-1, Es was reduced from 120 mm to 101 mm under rain-fed conditions and from 143 mm to 110 mm under irrigated conditions, and T was increased from 153 mm to 193 mm under rain-fed conditions and from 215 mm to 310 mm under irrigated conditions. Under rain-fed conditions, about 35% of evapotranspiration (ET) may be lost from the soil surface for the fertilized crops and 44% of ET for the unfertilized crops. Transpiration accounted for 65% of ET for the fertilized crops and 56% for the unfertilized crops under rain-fed. As a result of this, WUE was increased by 44% for dry matter and 29% for grain yield under rain-fed conditions, and by 60% for dry matter and 57% for grain yield under irrigated conditions. Transpiration efficiency for the fertilized crops was 43.8 kg ha-1 mm-1 for dry matter and 15 kg ha-1 mm-1 for grain yield, while TE for the unfertilized crops was 33.6 kg ha-1 mm-1 and 12.2 kg ha-1 mm-1 for dry matter and grain yield, respectively. Supplemental irrigation significantly increased post-anthesis water use, transpiration, dry matter and grain yield. Water-use efficiency for grain yield was increased from 9.7 to 11.0 kg ha-1 mm-1 by supplemental irrigation, although WUE for dry matter was not affected by it. Irrigation did not affect transpiration efficiency for grain yield, but decreased transpiration efficiency for dry matter by 16%. This was associated with higher harvest index as a result of good water supply in the post-anthesis period and increased transpiration under irrigated conditions.

Enhancing nitrogen use efficiency in crop plants

Abstract: Nitrogen is the most limiting nutrient for crop production in many of the world's agricultural areas and its efficient use is important for the economic sustainability of cropping systems Furthermore, the dynamic nature of N and its propensity for loss from soil‐plant systems creates a unique and challenging environment for its efficient management Crop response to applied N and use efficiency are important criteria for evaluating crop N requirements for maximum economic yield Recovery of N in crop plants is usually less than 50% worldwide Low recovery of N in annual crop is associated with its loss by volatilization, leaching, surface runoff, denitrification, and plant canopy Low recovery of N is not only responsible for higher cost of crop production, but also for environmental pollution Hence, improving N use efficiency (NUE) is desirable to improve crop yields, reducing cost of production, and maintaining environmental quality To improve N efficiency in agriculture, integrated N management strategies that take into consideration improved fertilizer along with soil and crop management practices are necessary Including livestock production with cropping offers one of the best opportunities to improve NUE Synchrony of N supply with crop demand is essential in order to ensure adequate quantity of uptake and utilization and optimum yield This paper discusses N dynamics in soil‐plant systems, and outlines management options for enhancing N use by annual crops